Project summary/abstract: Cytomegalovirus (CMV) is the most common congenital viral infection in pregnancy, affecting approximately 0.4-1% of live born infants. Congenital CMV can cause stillbirth and newborn death, or severe morbidity in the form of cognitive and motor delay, and most commonly, significant, progressive hearing loss. While classically it was thought that primary maternal CMV infection is associated with congenital infection, it has been found that in highly seropositive populations, a relatively large proportion of congenital infections result from maternal re- infection or re-activation. There is a gap in knowledge regarding the clinical and viral factors that contribute to viral activity among seropositive women in the United States. The long term goal of our research program is to curtail the occurrence and sequelae of congenital CMV infection. The objective of this application is to characterize the clinical and viral factors associated with ongoing CMV infection among seropositive women. This will be a prospective cohort study of viral dynamics in 240 seropositive women throughout gestation and at delivery. The project specific aims are: 1. Define the frequency, magnitude, and risk factors for maternal CMV viral shedding across gestation in CMV seropositive pregnant women. The working hypothesis is that low socioeconomic status, crowding in the home, exposure to young children, and hygienic risk factors will be associated with maternal viral shedding, which may indicate maternal re-infection. And 2. Profile shed viral populations and serologic response of CMV-seropositive pregnant women using next generation sequencing to differentiate re-infection versus re-activation. The working hypothesis is that re-infection with a new viral strain is responsible for more frequent shedding and higher mucosal viral loads than viral re-activation. The contribution of this project will be to characterize the clinical and viral factors associated with CMV reactivation or reinfection among seropositive women. This contribution will be significant because it will advance the field to identify a potential therapeutic target among pregnant women with CMV seropositivity. This work will allow development of a paradigm shift from the use of serology to a more accurate measure of disease activity.